A soft, supple and flexible skin has a marked cosmetic appeal and is an attribute of normal functioning epidermis. The outer layer of the epidermis, i.e. the stratum corneum, can however become inelastic and hard or flaky following exposure to adverse climate conditions. This can also be caused by excessive contact with detergents or solvents which result in a loss of skin moisture. Consequently, the skin loses its soft, supple and flexible characteristics.
It is therefore apparent that there exists a need for an effective treatment for skin which has become relatively inelastic and inflexible.
In an article of F Baiocchi, D Jennings and A J Del Vecchio in Cosmetics and Perfumery 90, 31-34 (1975) it is alleged that sodium stearoyl lactylates when incorporated in a hand cream or lotion result in a subjectively smooth and supple but not excessively greasy feeling when such creams or lotions are topically applied to the hands. The main reason for including these lactylates in hand and body cream formulations is that they act as very efficient emulsifiers.
In an article by L I Osipow et al in Drug Cosmet Ind, May 1969, 64 ff. it is disclosed that sodium stearoyl lactylate may be used in oil-in-water cosmetic creams as the emulsifier to impart body, lubricity and a pearlescent opacity to the cream. It is alleged that its absorption to the skin may enhance its softening action.
In another article by L J Murphy in Cosmetics and Toiletries 94, 43 ff (1979) the absorption of acyl lactylates on the skin was examined by using pig skin as a model. It is described that sodium isostearoyl lactylate (ISL) appears to reduce dryness and scaling of skin and restores a healthy texture to dry skin.
EP-B-278 370 (Kao) discloses specific acyl lactylates having alpha-branched acyl groups. This type of acyl lactylates is used in hair rinses and hair shampoos for their good hair conditioning action.
EP-A-442 708 (Unilever) discloses cosmetic compositions containing 2hydroxy alkanoic acids. Due to the presence of these acids in the compositions, several benefits are imparted to the skin, such as an increase in the elasticity of the skin, particularly of the stratum corneum. Similarly, EP-B-7 785 (Unilever) discloses cosmetical compositions comprising 2-hydroxy alkanoic acids, which also give various skin benefits when topically applied to the skin.
However, the extent to which the elasticity of skin can be enhanced by using these conventional actives is not satisfactory. Therefore, we have searched for other more effective actives. These actives should also be functional at pH values close to neutral which is often not the case with conventional skin elasticity increasing agents, eg. 2-hydroxy alkanoic acids, which require fairly acidic pH values to have a reasonable shelf life.
It has now been discovered that a narrow range of short chain acyl lactylates is able to provide these desired properties. Surprisingly, these acyl lactylates are capable of enhancing the elasticity of skin to a much greater extent than conventional actives when applied to the skin.